Around the Sky in 28 Days – Day 1

September 9, 2010

We are now a day past New Moon. A one-day old Moon can be easy to see depending on the time of the year. Unfortunately, this is the worst time of the year to see a one-day old Moon from the Northern Hemisphere.

The view below is for St. Louis, Missouri shortly after sunset. St. Louis was selected because of its central location. Observers from North America will see the Moon in roughly the same location (give or take a degree).

The reason the Moon is so hard to see in the evening is due to the shallow angle of the ecliptic relative to the horizon. In the chart below the ecliptic is the red line while the celestial equator is blue. In the spring the ecliptic is almost at a right angle to the horizon. This is why Mercury is easy to see in the evening during March/April and very difficult to see in the Fall.

View from Saint Louis, Missouri on the evening of Sept. 9. Created with Stellarium.

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Down south of the equator, the opposite is true. The ecliptic leaps out from the horizon. Below the chart is for Santiago, Chile but if usable for all of South America. Not only is the Moon easier to see but so is Venus and Mars. Even Saturn, which was lost to northern observers a few weeks ago, is still visible low in the west.

View from Santiago, Chile on the evening of Sept. 9. Created with Stellarium.

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Tomorrow the Moon gets easier to see as it joins Venus, Mars and Spica in a tight diamond formation.

If you have any pictures you’d like to share of the Moon in its travels, send them to <transientsky1@yahoo.com> and I’ll include them in future posts.